For the next Con I'm going to, a group of my friends and I are going to be going as zombie hunters because its a zombie themed con. Our cosplays are going to be blood stained and tattered but I'm having trouble finding a tutorial or even some decent pictures of how to tatter some clothing while making it look realistic.

Help, please? Or if you have any examples or advise I can look at that would be great. Anything on blood stains would be awesome too.

Con doesn't start til the 18th so I have time and we are going as zombie hunter versions of something but I want to leave it as a surprise ;3

I can help! Learning 'breakdown' was my favourite thing when I was in costume class at school. :3

For tattered clothing:
- use sandpaper and your own hands to create realistic-looking tears and rips. Scissors create too 'clean' a cut, so use them only to create little holes to start where you want the damage to be, then just RIP as you need.
- if you are VERY CAREFUL, you can also use a lighter to actually burn clothing. Not recommended if you're working with cotton because fire EATS that fabric right up. Polyester and wool gives a good look and the flame spreads slowly and eventually goes out on its own, but the smell of these fabrics being burned isn't pleasant.
- if you want a burned look without the risk, rip the fabric in a random pattern, and then do a thin drybrush brushstroke across the tear with a dark brown acrylic paint.

For dirt, blood, stains:
- TEA. Use any store-brand black tea in baggies to give things a nice overall old yellowed stain look.
- dirt and grass stains can be done easily with green and brown acrylic paint. For the green, it's best to dilute with water in order to give it the realistic faded look.
- blood can be done in many ways. If you want fresh-looking stains, corn syrup and red food dye is never wrong. It would also be a good idea to look at pre-made fake blood at costume stores and experiment with that. I use this stuff and it works great on clothing for permanent stains. If you want the blood to look crustry and aged, strokes with, you guessed it, acrylic paint works as well, alternating between drybrush strokes and globs in a darker, rusty colour.
- if you want the stains to look like smears, you can go to town with a big wet paintbrush or even finger-paint. For splatters, lay down the garment on newspaper or tarp or a surface you don't mind getting dirty, load up a big paintbrush with either the fake blood or dirt, and flick the brush just above the surface of the garment. The droplets and spray from the brush will splatter pretty realistically. Use more paint globs and more aggressive flicking motions for bigger splatters.
- if you want to get really gross, you can use cut up pieces of sponge and soak them in paint or fake blood to create chunky textures that emulate splattered brains or even vomit. You can use your imagination with colour and consistency on that one.

Hopefully this helps, good luck!

EDIT: Just in case I sound like a crazy lady, here's some examples of breakdown and weathering I've done on costumes:

what I did was cut some little snips with scissors and then rip the fabric by hand. Then I took some gardening dirt and rubbed in all over. I used a damp paper towel to smear it on the front. My zombie was pushed down and dragged on the knees, so I was trying to get that look. Then I used 2 blood mixes to gore it up a bit.

The more dried streaked lighter blood is:
1/4 cup water
4 TBSP corn syrup
8 drops of red food coloring (I used gel)
2 drops yellow food coloring
2 drop green food coloring
I put that mix in an emtpy water bottle and poured it on in various places.

I used an exacto knife to cut my Highschool of the Dead shirt. Sometimes I would lightly graze the fabric or messily cut out a hole. As for blood, I mixed red, brown, and black acrylic paint and covered my hands with it and balled up my shirt with my dirtied hands.HOTD 1HOTD 2

Light tattering and wear can be done with some heavy grit sandpaper on places that you might touch every day. I think that's probably the best piece of advice I can give you on making clothes tattered and grungy: think about places that wear out first: knees, cuffs/hems, pockets/belt loops, elbows depending on the garment. Think about places you might wipe your hands off on and the direction.

The thing about using sandpaper to weather pockets on a jumpsuit, let's say, hypothetically, is that you can very easily sand through the thread as well as the fabric. Then you have a nice distressed pocket that isn't attached any more. :-( It's great advice, just be careful.
Other things I've done include using old bicycle chains and cooking spray as sources of grease. Smear and spray the garment, let it sit overnight, then wash it with soap. The grease will stain but the actual greasiness is gone.

For my Shiro cape I first cut some holes, used a lot of sandpaper to make look it realistic and not like a straight cut. Then I splattered it with some store bought fake blood and let it dry. After that I dug up some dirt in my back yard, tossed the cape on the ground and jumped on it, twirled it around and scraped it in the dirt. Then I let it dry, brushed of the excess dirt and repeated. And as a final finish I dragged it on the grass to make some green-ish stains.
I must say that it looked very realistic at the and. And I was afraid that it would smell horrible, but it only smelled of grass. Here's a picture.